Staple processing device



Dec. 7, 1954 w. o. CHRISTY 2,696,147

STAPLE PROCESSING DEVICE Filed Oct. 15, 1949 INVENTOR.

ATTORNEY Failed. 7.

This invention-relatesto the treatment of fibrous material with liquids.It relates to. -the-.purification of staple rayon and, moreparticularly,to an improved method and apparatus for opening the wet chips andpresenting all the staple fibers to uniformliquid purification. -Rayonstaple is commonly produced by extruding visc ose throughlarge-spinnerets,-each having several thousand holes, and quite a few ofthe filament bundles thus formed'are collected together as'a towcomposed of 100,000 filaments,-more-or less, which maybe processed assuch and then cut into staple lengths before drying. Alternatively the:tow may be cut in either the acid state before any-washing orpurification treatment or after a preliminaryvvash toremove thecoagulating bath ingredients and some of the by-products formed inspinning. -There are certaininherent advantages in cutting the filamentsinto staple lengths before substantial puri fication but there isdifliculty in uniformly and efficiently purifying-the fibers in thisform. Probably the most important advantage of -staple fiberpurification rather than tow purification is getting retentive crimp inthe fibers which naturally arises from the individual fibers being in arelaxed state during purification. On the other hand, difiiculty incompletely opening the dense chips and presenting -the fibers therefromuniformly to processing liquids whereby to obtain satisfactorilypurified fiber has been a bafiling problem over many years. Numerousmethods and means have been proposed and some of these have beenpartially effective in overcoming the inherent difficulty of staplefiber processing. The known prior art methods and equipment fail toreduce the compact chips completely to individual loosened fibers andrequire exceptionally long purification cycles and result in anon-uniform processed product, Then too, if the fibers released from thechips are too violently worked, they may and have frequently becometangled and form neps and rat tails or strings which militate againstsatisfactory subsequent processing.

It is important that the chips of cut staple, be quickly and completelyeliminated but without tangling of the fibers. The free fibers shouldthen be formed into a uniform blanket which will allow slow uniformpassage of processing liquid without channeling. The change from densechips-to -a-satisfactory blanket of individual fibers should take placequickly with a minimum of space and equipment if the processis to beoperated economically and efiiciently for until this blanket of releasedfibers is formed, satisfactory purification cannot continue.

An object of this invention is to provide an improved process andapparatus for treating a fibrous material with liquid. -Another objectis the provision of apparatus and process for converting wet staplerayon chips 'to individual fibers and immediately forming the freefibers into a uniform blanket which can be effectively treated withprocessing liquid. Other objects will be apparent from the descriptionthat follows.

The objects of this invention are accomplished by feeding the fibrousmaterial to be treated to a sluice containing the liquid and passing itfrom there, preferably through a conduit having an oscillating outletend, into a slurry box which has an open bottom section and which issituated over an endless perforated conveyor belt. The liquid is drainedout of the fibrous material by passing the wet mass in the box onto theperforated conveyor belt and then between a roller, which closes one endof the box, and the conveyor belt thereunder. The bottom opening in thebox may be adjustable by means ICC 2 of arretractable bottom the;adjustment of which permits the volume of fibrous material/liquidmixtureto be'varied so that uniform treatment is assured... This opening, for agiven operation, may be. set..or.. fixed and maintained at the desiredsetting during continuous operation. The setting of the open section andthe clearance between the roller and belt. will, of. course, dependupon.the

blanket thickness desired. In the case of .staple rayon.

chips, the chips are softened and. opened in. thesluice and also in .theslurry box. The oscillating tailpipe permits uniform distribution .of.slurry in the box .and the opening, in the slurrybox bottompermitsnecessary drainage for suitable blanketformationh In the figures below,which are given for illustrative purposes only,

. Figure l is a plan line AA of and Figure 2 is a side elevation partlyin section;

As shown, wet, preliminary washed chips 1 ofstaple lengths are suppliedfrom awet, cutter (not shown) by means of. a conveyor). to one end ofthe sluice box 3. At about the same point, throughconduit 4adilute-aqueous solution of caustic soda is brought into the boxat asufficient rate of flow to carry the chips to the other end of the uppersection 5 of the box and the softened chips and liquid are dischargedthrough opening 6 to the lower section 7 of the slicebox through'whichthey flow in the reverse direction. This reversal of flow and theturbulence that accompanies it causes the chip'sto loosen up and bythetime the staple; has reached the discharge end 8 of the lower runthey are partially opened. Again, the passage of this. slurry throughthe oscillating tail pipe 9 with its attendant bendssubstantiallycompletes the job of breaking up-thechips-and delivers substantiallyseparated fibers to the slurry box 10. The oscillating tailpipe may beoperated by a motor or-any convenient manner (not shown); Actually,oscillation is not necessary and a stationary tailpipe can be used. 1

- Slurry box 10 is built with two side boards and a board across theinlet end, while a driven roller 11 is provided to close the exit end ofthe box. This roller may be independently driven or,.preferably, it maybe driven by a drive interlocked either mechanically or electricallywith the conveyor belt-drive. "The box 10 is supported over theperforated or screen conveyor 12 andis also provided with a bottom plate13 partially covering the screen under the box. The slurry box clearsthe conveyor by about /8 of an inch. The bottom plate may be adjustableor not. The box lies very close to the belt but preferablydoes not rideon the belt. Due to the. oscillations of the tail pipe 9 the slurry isuniformly fed across the full width of the slurry box 10. Due to theclosed bottom near the entrance end and the'open portion further along,the fibers have a chance to-complete separation and to settle down in anevenly distributed form by the time the conveyor screen 12 carries thesoaking wet mass of fibers to the vicinity of theroll 11. 'This rollsqueezes and condenses the fiber mass to form a blanket 14 of quiteuniform texture, which may subsequently pass under desulfuring, washing,bleaching, and/0r finishing showers before final squeezing, fiufiing anddrying. The uniform flow over the draining [section results in a blanketof uniform thickness.- The liquid draining from the fibers may berecovered by using a-tank 15 or standard sumps and recirculating pumps.V

The slurry box 10 is designed in accordance with slurry consistency.With a slurry formed using 105 gal/min. of 0.5% sodium hydroxide at C.and 17 lbs/min. of 1.5 denier/filament chips (or 20.1 lbs/min. of 3.0d./f. chips or 20.8 lbs/min. of 5.5 d./f. chips, all on 11% regainbasis), the slurry box is designed and set so that a retention of theslurry in the box for about one minute is accomplished. Under the aboveconditions retention for 0.5 minute is insufficient. With thinnerslurries less retention is necessary. Of course, the length of thesluice, the number of spinneret holes on the spinning machine, etc.,each have their effect on the retention time required in the slurry boxfor optimum opening. Such factors are, of course, considered in thedesign of the apparatus.

The use of dilute caustic solution in forming the chip slurry serves adual purpose of a liquid vehicle to swell the fibers and soften thechips as well as to initiate desulfuring action on the washed staplefibers. This solution could be substituted by plain water or by a sodiumcarbonate, sodium sulfide or other desulfuring solutions as desired.Obviously, this early use of a desulfuring reagent speeds up the processand is an economic expedient.

Because the conveyor screen runs under the slurry box, which is providedat the entrance zone of the fiber slurry with a bottom plate, there is aspace where the fibers can finally turn and work apart and recomposethemselves into a well distributed voluminous mass while provided withthe necessary liquid vehicle. Subsequently, when the liquid drains fromthe slurry through the screen of the conveyor after the bottom plate nolonger covers the screen, the fibers become rematted in a randomarrangement and when compacted by the roll 11 from a uniformly perviousblanket.

By having the side boards of this box relatively high and the end rollof proportionally large diameter a rather deep bed of slurry is held inthe box. This better insures the formation of a good processibleblanket. The roll is preferably positively driven in the directionshown, although it may be frictionally driven or held stationary. Ifstationary, much more power will be required to drive the conveyor.

In U. S. Patent 2,337,068 there is disclosed a trough through which ascreen conveyor carrying a blanket of fibers passes. The trough retainsthe liquid in an effort to soak to a greater extent the fibers making upthe blanket. the trough by the sides and bottom of the trough and by therollers at either end. It is necessary to retain the liquid in thismanner in order to get uniformity throughout the blanket. This means ofhandling might well be necessary if the blanket of fibers is poorlyformed, nonuniform in porosity or, in general, too impervious. With theimproved blanket obtained by the method above described, such a treatingtrough used in combination with a conveyor belt carrying the blanket isnot only unnecessary in subsequent purification steps but would be anactual process hindrance. This is because the stock in the improvedblanket in accordance with this invention is so well opened that itsoaks up the treatment liquid bodily and allows it to drain through theblanket effectively, when it is applied either by means of a spray orshower pan, instead of shedding the liquid from the surface and allowingit to escape ineffectively through the side walls of the conveyor. Thus,the porous nature of the improved blanket of this invention serves tohold the treatment liquids long enough for adequate, uniform processingwithout any liquid-confining apparatus.

This invention permits the shower pan to be replaced by spray pipes andthe use of one-third less solution per pound of production with greatlyimproved uniformity of purification, finish application, etc. increasesin capacity for each conveyor amounting to as much as 50% and the dryercapacity is increased by at least 10% because the blanket contains fewerunopened chips. Quality is improved as shown by a 10% increase (on 1.5d./f. stock) in cohesion as measured by the draw sliver tenacity.

By the use of the apparatus and process of this invention the quantityand quality of cut stock processed are appreciably increased. Thickspots, which are bypassed by purification solution, and thin spots,which drain excessive amounts of solution, are avoided. By adjusting thedrainage space between the retractable bottom 13 and the forming roll11, the height of the slurry in the box 10 is regulated to cause auniform flow over the draining section. This results in a blanket ofuni- In this case the treatment liquid is retained in The inventionallows r form thickness. The decrease in rat-tails and strings makes theblanket very easy to pull apart.

While this invention has been described with particular reference tostaple rayon chips, it is not limited thereto. Various fibrous materialsmay be treated in the apparatus of this invention, including those ofsynthetic polymers such as polyamides, polyacrylonitriles, etc. or otherproducts such as wool, silk, cellulose acetate, cotton, asbestos, etc.

Similarly, the invention is not limited to the particular form shown.For example, the bottom of the slurry box may be made stationary and theroller adjustable to permit a greater or lesser amount of screening tooccur. The roller may also be adjustable in the vertical direction topermit variation in blanket thickness. Further, the end of the boxopposite the roller may be oblique or inclined to the belt, andadjustable so that the distance between its bottom edge and the rollercould be varied. Still further, the path to the slurry box may be longeror more tortuous, if desired.

By the process and apparatus of this invention the number of unopenedchips is markedly reduced and the occurrence of hard, compact unopenedchips is eliminated. In standard blankets about 60% by weight of thestock can be segregated as chips many of which are hard and compact. Inthe improved blanket obtained by this invention, only about 40% byweight can be identified as chips and all of these are soft, fiutfychips, the structure of which permits ready and adequate penetration ofprocess liquids and the attainment of crimped form. The hard, compactunopened chip characteristic of standard blankets is advantageouslyeliminated.

Any departure from the procedure described herein which conforms to theprinciples of the invention is intended to be included within the scopeof the claim below.

I claim:

Apparatus for converting staple chips of regenerated cellulose fibersinto individual fibers laid down in blanket form without appreciableentanglement of the individual fibers which comprises a sluice boxhaving upper and lower sections in substantially horizontal position; atthe entrance end of said upper section for said chips, an inlet for anaqueous liquid; means for reversing the direction of fiow of liquid atthe opposite end of said upper section comprising a conduit to dischargesaid liquid and said fibers substantially vertically downward into saidlower section and means directing the flow in said lower section in adirection opposite to the direction of flow in said upper section; aslurry box mounted above a perforated conveyor belt; an oscillatingconduit for discharging said liquid and fibers from said lower sectionuniformly into said slurry box, said box having a roller at itsdischarge end and said box having a bottom plate above and partiallycovering said belt, said roller and said belt providing means to pressthe fibers into said blanket on said belt as said belt passes out frombeneath said box.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,277,737 Lefebvre Sept. 3, 1918 1,610,742 Bucking Dec. 14,1926 1,708,724 Haug d. Apr. 9, 1929 1,753,800 Millspaugh Apr. 8, 19302,504,744 Sproull et al. Apr. 18, 1950 FOREIGN PATENTS Number CountryDate 384,308 Italy Dec. 10, 1940

